I wonder why they don't use any dampening? Is it better with nothing?.
Yup. Anything behind the HE-500 drivers totally kills the bass and many other aspects of the sound.
You know how when you put your hands behind Grado cups and it does the same?... with HE-500 drivers you notice it when you pur your hands NEAR the backs of the cups... not even touching the headphone.
They REALLY need to be completely open-air to sound their best.
I'm also using the fuzzor mod and leather Odin pads. Sorbothane made no noticeable difference, so I don't use any.